The present invention relates to a method and apparatus for sensing the passage of a moving element, and more particularly provides apparatus for detecting the rotation of the dial arm of a utility meter.
Metering devices are used by utility companies to register the amount of energy, water, etc. consumed by residential and commercial users. These utility meters generally are mechanical devices having a meter face with a number of dials disposed thereon, registering utility usage in increments of tens, hundreds, thousands, etc. Such utility meters, most notably gas meters, are generally located within the private dwellings of the residential customers and are therefore not readily accessible to utility company employees. The meter readings must be periodically taken, however, in order to ascertain the amount of utility usage and thus determine the appropriate bill to be forwarded to the customer.
It has therefore been long recognized that it would be desirable if the utility meter were mounted external to the dwelling, whereby the utility meter reader would have continual access to the meter and the customer would be free of the obligation to permit strangers to enter their homes. Unfortunately, it would be prohibitively expensive to replace existing utility meters with other meters capable of being read from outside the customers residence.
One other method of accomplishing the same goal would to provide a retrofit device connectable to existing utility meters and designed to be read externally from outside of the customers residence. Such a device would presumably be coupled to the existing meter and would provide electrical signals indicative of utility usage. The electrical signals could then be communicated to the outside of the residence by ordinary wires. In order to be successful, the retrofit device would have to be inexpensive to manufacture, simple to install, and reliable in its operation. No such device has yet appeared on the market.